How to make Modifier panel visible in Toolshelve
The panel displaying the modifiers includes methods with names matching every modifier type that are used to display the properties of the matching modifier, getattr() is used to find the matching method based on the type of modifier in the objects modifier list.

While inheriting the modifiers panel directly causes issues, you can create a local instance of the panel and make use of the methods it contains.

import bpy
from bl_ui.properties_data_modifier import DATA_PT_modifiers

class myModifiersPanel(bpy.types.Panel):
    bl_label = "Object Modifiers"
    bl_idname = "OBJECT_PT_mymodifiers"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_category = "Modifiers"

    def draw(self, context):
        mp = DATA_PT_modifiers(context)
        layout = self.layout
        ob = context.object
        row = layout.row()

        if not ob.modifiers:
            row.label('No modifiers')
        else:
            for md in ob.modifiers:
                box = layout.template_modifier(md)
                if box:
                    getattr(mp, md.type)(box, ob, md)

def register():
    bpy.utils.register_class(myModifiersPanel)

def unregister():
    bpy.utils.unregister_class(myModifiersPanel)